The Talmud in מסכת הרכות teaches the concept that the צדיקים, the righteous, even in their death are considered alive. The רשעים, the evil, even while they are alive are considered dead.
The Maharal explains this idea as follows. Hashem expects that man be a giving individual. We are to emulate Hashem’s example of kindness and caring and taking care of the needs of the downtrodden. In essence, we are to be constantly giving of ourselves to help others. The צדיק epitomizes this idea as he is completely devoted to עם ישראל. Therefore, when they leave this world, they continue giving as their legacy lives on and their disciples continue to live by their example.
The רשע, on the other hand, never gives of himself and takes and takes wherever he can. Even when alive, he is considered dead, as he contributes nothing to benefit man.
This is a valuable lesson. This also explains why selfish people cannot find happiness. They never give of themselves.